Heterodimetallic Germanium(IV) Complex Structures with ... · Heterodimetallic Germanium(IV)...

Heterodimetallic Germanium(IV) Complex Structures with TransitionMetals

Fa-Nian Shi, † Luıs Cunha-Silva, † Michaele J. Hardie, ‡ Tito Trindade, † Filipe A. Almeida Paz, † andJoao Rocha* ,†

Department of Chemistry, UniVersity of AVeiro, CICECO, 3810-193 AVeiro, Portugal and Schoolof Chemistry, UniVersity of Leeds, Leeds LS2 9JT, United Kingdom

Received March 15, 2007

The hydrothermal synthesis and structural characterization of a number of complex compounds containing thedivalent tris(oxalato-O,O′)germanate anion, [Ge(C2O4)3]2-, or the neutral bis(oxalate-O,O′)germanium fragment,[Ge(C2O4)2], with transition-metal (M) cationic complexes of 1,10′-phenanthroline (phen) is reported: [M(phen)3]-[Ge(C2O4)3]‚xH2O [where M2+ ) Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), Co2+ (4); x ) 0.2 for 2b], [MGe-(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)]. The isolation of two polymorphs with Cu2+ (1a and1b) and other pseudo-polymorphs for Fe2+ (2a and 2b) was rationalized based on slightly different molar ratios forthe starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IRand FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basisof single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series ofcompounds was discussed on the basis of the various intermolecular interactions present (strong C−H‚‚‚π andweak C−H‚‚‚O hydrogen-bonding interactions, C−H‚‚‚π and π−π contacts).

Introduction

In recent years, research on crystalline organic-inorganichybrid oxalates has gained great interest in materials sciencedue to the structural diversity of these compounds whichrange from discrete complexes1-4 to 1D chains,5-7 2Dlayers,8,9 and 3D open frameworks.10-12 Moreover, some of

these materials find interesting potential applications arisingfrom their peculiar architectures such as zeolite-like frame-works13 and the inherent properties of the metallic centers,for example, photoluminescence arising from the presenceof lanthanides.14

Following our ongoing research on crystalline the hybridmaterials,15-25 we recently focused our attention on the use

* To whom correspondence should be addressed. Phone: (+351) 234370730. Fax: (+351) 234 370084. E-mail: [email protected].

† University of Aveiro.‡ University of Leeds.

(1) Cangussu, D.; Stumpf, H. O.; Adams, H.; Thomas, J. A.; Lloret, F.;Julve, M. Inorg. Chim. Acta2005, 358, 2292-2302.

(2) Armentano, D.; De Munno, G.; Lloret, F.; Julve, M.CrystEngComm2005, 7, 57-66.

(3) Carranza, J.; Grove, H.; Sletten, J.; Lloret, F.; Julve, M.; Kruger, P.E.; Eller, C.; Rillema, D. P.Eur. J. Inorg. Chem.2004, 4836-4848.

(4) Vaidhyanathan, R.; Natarajan, S.; Rao, C. N. R.Dalton Trans.2001,699-706.

(5) Zhang, Q. Z.; Yang, W. B.; Lu, C. Z.J. Chem. Crystallogr.2006, 36,225-228.

(6) Yang, S. H.; Li, G. B.; Tian, S. J.; Liao, F. H.; Lin, J. H.Eur. J.Inorg. Chem.2006, 2850-2854.

(7) Garcia-Couceiro, U.; Castillo, O.; Luque, A.; Garcia-Teran, J. P.;Beobide, G.; Roman, P.Eur. J. Inorg. Chem.2005, 4280-4290.

(8) Zhang, L.; Ge, Y. Y.; Peng, F.; Du, M.Inorg. Chem. Commun.2006,9, 486-488.

(9) Manna, S. C.; Zangrando, E.; Drew, M. G. B.; Ribas, J.; Chaudhuri,N. R. Eur. J. Inorg. Chem.2006, 481-490.

(10) Tsao, C. P.; Sheu, C. Y.; Nguyen, N.; Lii, K. H.Inorg. Chem.2006,45, 6361-6364.

(11) Mohanu, A.; Brouca-Cabarrecq, C.; Trombe, J. C.J. Solid State Chem.2006, 179, 3-17.

(12) Chapelet-Arab, B.; Nowogrocki, G.; Abraham, F.; Grandjean, S.J.Solid State Chem.2005, 178, 3055-3065.

(13) Mahe, N.; Audebrand, N.Solid State Sci.2006, 8, 988-999.(14) Song, J. L.; Mao, J. G.Chem. Eur. J.2005, 11, 1417-1424.(15) Soares-Santos, P. C. R.; Paz, F. A. A.; Ferreira, R. A. S.; Klinowski,

J.; Carlos, L. D.; Trindade, T.; Nogueira, H. I. S.Polyhedron2006,25, 2471-2482.

(16) Shi, F. N.; Paz, F. A. A.; Girginova, P.; Rocha, J.; Amaral, V. S.;Klinowski, J.; Trindade, T.J. Mol. Struct.2006, 789, 200-208.

(17) Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T.; Shi, F. N.; Mafra,L. Prog. Solid State Chem.2005, 33, 113-125.

(18) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Nogueira, H. I. S.; Rocha,J.; Amaral, V. S.; Klinowski, J.; Trindade, T.J. Solid State Chem.2006, 179, 1497-1505.

(19) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Amaral, V. S.; Rocha, J.;Klinowski, J.; Trindade, T.Inorg. Chim. Acta2006, 359, 1147-1158.

(20) Mafra, L.; Paz, F. A. A.; Shi, F. N.; Fernandez, C.; Trindade, T.;Klinowski, J.; Rocha, J.Inorg. Chem. Commun.2006, 9, 34-38.

(21) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Mafra, L.; Amaral, V. S.;Rocha, J.; Makal, A.; Wozniak, K.; Klinowski, J.; Trindade, T.J. Mol.Struct.2005, 754, 51-60.

Inorg. Chem. 2007, 46, 6502−6515

6502 Inorganic Chemistry, Vol. 46, No. 16, 2007 10.1021/ic700507j CCC: $37.00 © 2007 American Chemical SocietyPublished on Web 07/10/2007

of germanium centers.26,27 These often exhibit two distinctoxidation states,+2 and+4, with the latter being the moststable at ambient conditions and commonly appearing ininorganic compounds (such as GeO2) and germanate frame-works.28,29 In addition, Ge4+ centers exhibit a number ofdistinct coordination numbers and environments, namely,four (often tetrahedral),30-32 five (square pyramidal ortrigonal bipyramidal),31,33-36 and six (often octahedral),37,38

a crucial feature in order to achieve topological diversity forthe frameworks.

Here we wish to report the first complex-based heterodi-metallic crystalline compounds containing the divalent tris-(oxalato-O,O′)germanate anion crystallizing with a numberof transition-metal (M) complexes with 1,10′-phenanthroline(phen) organic residues, [M(phen)3][Ge(C2O4)3]‚xH2O [whereM2+ ) Cu2+ (1a and1b), Fe2+ (2a and2b), Ni2+ (3), Co2+

(4); x ) 0.2 for 2b (Scheme 1). Furthermore, the firstexamples of binuclear complexes containing the neutral bis-(oxalate-O,O′)germanium fragment [Ge(C2O4)2] are reported,

which is instead connected by twoµ2-bridging hydroxylgroups to a cationic [M(phen)2]2+ fragment, [MGe(phen)2-(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)](Scheme 2). For the former series of compounds, twopolymorphs for Cu2+, and a pseudo-polymorph for Fe2+

could be isolated by employing slightly different syntheticprocedures. Remarkably, searches in the literature and theCambridge Structure Database (CSD, Version 5.28 Nov2006)39,40reveal that only a handful of structures containing[Ge(C2O4)3-x]2(x-1) moieties are known to date, all comprisingsmall organic molecules or K+ as the counterions.41-44

Experimental Section

General. Chemicals were readily available from commercialsources and used as received without further purification: amor-phous germanium(IV) oxide (GeO2, 99.99+%, Aldrich), oxalic aciddihydrate (H2C2O4‚2H2O, g99%, Panreac), 1,10′-phenanthrolinemonohydrate (phen, C12H8N2‚H2O, g99.0%, Fluka), copper(II)acetate monohydrate (CuC4H6O4‚H2O, 98%, Panreac), nickel(II)acetate tetrahydrate (NiC4H6O4‚4H2O, g99%, Riedel-deHae¨n),cobalt(II) acetate tetrahydrate (CoC4H6O4‚4H2O, 98%, Panreac),cadmium(II) acetate dihydrate (CdC4H6O4‚2H2O, 98%, Fluka),ammonium ferrous sulfate hexahydrate [(NH4)2Fe(SO4)2‚6H2O,99%, Merck], and potassium ferric oxalate [KFe(C2O4)2, 99%,Ventron].

Instrumentation. Elemental analyses for C, H, and N wereperformed in a CHNS-932 elemental analyzer in the MicroanalysisLaboratory of the University of Aveiro.

Thermogravimetric analyses (TGA) were carried out using aShimadzu TGA 50 with a heating rate of 5°C/min under acontinuous flow of air with rate of 20 cm3/min.

Scanning electron microscopy (SEM) and energy dispersiveanalysis of X-rays spectroscopy (EDS) were performed using aHitachi S-4100 field emission gun tungsten filament instrumentworking at 25 kV. Samples were prepared by deposition onaluminum sample holders and were carbon coated.

FT-IR spectra were collected from KBr pellets (Aldrich, 99%+,FT-IR grade) on a Mattson 7000 FT-IR spectrometer. FourierTransform Raman (FT-Raman) spectra (range 4000-100 cm-1)

(22) Shi, F. N.; Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T.Inorg.Chim. Acta2005, 358, 927-932.

(23) Girginova, P. I.; Paz, F. A. A.; Nogueira, H. I. S.; Silva, N. J. O.;Amaral, V. S.; Klinowski, J.; Trindade, T.Polyhedron2005, 24, 563-569.

(24) Paz, F. A. A.; Klinowski, J.J. Solid State Chem.2004, 177, 3423-3432.

(25) Paz, F. A. A.; Shi, F. N.; Klinowski, J.; Rocha, J.; Trindade, T.Eur.J. Inorg. Chem.2004, 2759-2768.

(26) Mafra, L.; Paz, F. A. A.; Shi, F. N.; Rocha, J.; Trindade, T.; Fernandez,C.; Makal, A.; Wozniak, K.; Klinowski, J.Chem. Eur. J.2005, 12,363-375.

(27) Mafra, L.; Almeida Paz, F. A.; Shi, F. N.; Sa´ Ferreira, R. A.; Carlos,L. D.; Trindade, T.; Fernandez, C.; Klinowski, J.; Rocha, J.Eur. J.Inorg. Chem.2006, 47-41-4751.

(28) Greenwood, N. N.; Earnshaw, A.Chem. Elements, 2nd ed.; Butter-worth-Heinemann: Oxford, U.K., 1997.

(29) Cotton, F. A.; Wilkinson, G.AdVanced Inorganic Chemistry, 5th ed.;John Wiley & Sons: New York, 1988.

(30) Karlov, S. S.; Lermontova, E. K.; Zabalov, M. V.; Selina, A. A.;Churakov, A. V.; Howard, J. A. K.; Antipin, M. Y.; Zaitseva, G. S.Inorg. Chem.2005, 44, 4879-4886.

(31) Schnepf, A.Eur. J. Inorg. Chem.2005, 2120-2123.(32) Iwamoto, T.; Masuda, H.; Ishida, S.; Kabuto, C.; Kira, M.J. Am. Chem.

Soc.2003, 125, 9300-9301.(33) Chen, L.; Chen, J. X.; Sun, L. J.; Xie, Q. L.Appl. Organomet. Chem.

2005, 19, 1038-1042.(34) Khrustalev, V. N.; Portnyagin, I. A.; Borisova, I. V.; Zemlyansky, N.

N.; Ustynyuk, Y. A.; Antipin, M. Y.; Nechaev, M. S.Organometallics2006, 25, 2501-2504.

(35) Takeuchi, Y.; Tanaka, K.; Tanaka, K.; Ohnishi-Kameyama, M.;Kalman, A.; Parkanyi, L.Chem. Commun.1998, 2289-2290.

(36) Holmes, R. R.; Day, R. O.; Sau, A. C.; Poutasse, C. A.; Holmes, J.M. Inorg. Chem.1985, 24, 193-199.

(37) Shen, X.; Nakashima, A.; Sakata, K.; Hashimoto, M.Inorg. Chem.Commun.2004, 7, 621-624.

(38) Krivokapic, A.; Anderson, H. L.; Bourhill, G.; Ives, R.; Clark, S.;McEwan, K. J.AdV. Mater. 2001, 13, 652-656.

(39) Allen, F. H.Acta Crystallogr., Sect. B2002, 58, 380-388.(40) Allen, F. H.; Motherwell, W. D. S.Acta Crystallogr., Sect. B2002,

58, 407-422.(41) Seiler, O.; Burschka, C.; Penka, M.; Tacke, R.Z. Anorg. Allg. Chem.

2002, 628, 2427-2434.(42) Dean, P. A. W.; Dance, I. G.; Craig, D. C.; Scudder, M. L.Acta

Crystallogr., Sect. C2001, 57, 1030-1031.(43) Martin, L.; Turner, S. S.; Day, P.; Guionneau, P.; Howard, J. A. K.;

Uruichi, M.; Yakushi, K.J. Mater. Chem.1999, 9, 2731-2736.(44) Jorgensen, N.; Weakley, T. J. R.Dalton Trans.1980, 2051-2052.

Scheme 1 Scheme 2

Heterodimetallic Germanium(IV) Complex Structures

Inorganic Chemistry, Vol. 46, No. 16, 2007 6503

were recorded on a Bruker RFS 100 spectrometer with a Nd:YAGcoherent laser (λ ) 1064 nm).

Synthesis of [Cu(phen)3][Ge(C2O4)3] (1a). A mixture containing0.06 g of GeO2, 0.18 g of H2C2O4‚2H2O, 0.10 g of CuC4H6O4‚H2O, and 0.20 g of phen was mixed in ca. 15 g of distilled waterand stirred at ambient temperature for 30 min. The resultinghomogeneous suspension, with approximate molar composition of1:3:1:2, respectively, was transferred to an autoclave (ca. 40 mL)and heated at 100°C for 72 h. Large single crystals of [Cu(phen)3]-[Ge(C2O4)3] were directly obtained from the autoclave contentsalong with some small impurities (later identified as compound6,see below) which could not be eliminated by physical separation.The sample was washed with copious amounts of distilled water,filtrated, and air-dried under ambient conditions (yield 49.0% basedon CuC4H6O4‚H2O).

Calculated elemental composition (based on single-crystal datafor C42H24N6O12CuGe, MW 940.80; %): C 53.62, N 8.93, H 2.57.Found for the as-synthesized bulk material (%): C 49.49,N 8.39, H 2.41. TGA data (weight losses inside parentheses):205-341 °C (-40.7%); 341-599 °C (-35.3%). Selected FT-IRand Raman (inside parentheses and in italics) data (in cm-1):ν(C-H, aromatic) ) 3068w, 2933w, (3073); ν(uncoordinatedcarbonyl groups)) 1735s;νasym(-CO2

-) ) 1676s, 1627m, 1588w,(1606, 1545); ν(C-C, skeletal vibrations)) 1518m, 1497w, (1446);δ(C-H) ) 1428s, (1411); νsym(-CO2

-) ) 1428s, 1362s, 1330s,(1411); ν(C-N, heteroaromatic amines)) 1330s; ν(C-O) )1226m, 1198w, 1146w, (1296); ν(C-C skeletal stretching mode)) 1105w, (1054); ν(C-H) ) 992w;ν(C-C and Ge-O) ) 893w,845m, 819s, (807); δ(CO2

-) ) 775w, 725s, (721); γ(C-H) )644w, 595w;ν(M-N) andF(CO2

-) ) 470m, 426w, (427).Synthesis of [Cu(phen)3][Ge(C2O4)3] (1b). The synthetic pro-

cedure used to isolate this polymorph is identical to that describedfor 1a but using instead a reaction mixture containing 0.050 g ofGeO2, 0.180 g of H2C2O4‚2H2O, 0.095 g of CuC4H6O4‚H2O,0.300 g of phen, and 15 g of H2O (approximate molar compositionof 1GeO2:3H2C2O4:1CuC4H6O4:3phen). Yield 95.6% based onCuC4H6O4‚H2O.

Calculated elemental composition (based on single-crystal datafor C42H24N6O12CuGe, MW 940.80; %): C 53.62, N 8.93, H 2.57.Found (%): C 53.50, N 8.72, H 2.54. TGA data (weight lossesinside parentheses): 201-343°C (-48.0%); 343-599°C (-31.9%).Selected FT-IR and Raman (inside parentheses and in italics) data(in cm-1): ν(C-H, aromatic)) 3059w, (3069); ν(uncoordinatedcarbonyl groups)) 1737s;νasym(-CO2

-) ) 1669w, 1621w, 1588w,(1624, 1605, 1586); ν(C-C, skeletal vibrations)) 1515m, 1493w,(1449); δ(C-H) ) 1425m, (1416); νsym(-CO2

-) ) 1425m, 1318s,(1416, 1307); ν(C-N, heteroaromatic amines)) 1318s, (1307);ν(C-O) ) 1225m, 1191w, 1139w;ν(C-C skeletal stretchingmode)) 1102w, (1053); ν(C-H) ) 1000w, 965w;ν(C-C andGe-O) ) 892m, 853m, 821s;δ(CO2

-) ) 778w, 724m, (735);γ(C-H) ) 645w, 593w;ν(M-N) and F(CO2

-) ) 470m, 420w,(425).

Synthesis of [Fe(phen)3][Ge(C2O4)3] (2a). The synthetic pro-cedure used to isolate [Fe(phen)3][Ge(C2O4)3] is identical to thatdescribed for1a with the reaction mixture containing instead0.050 g of GeO2, 0.140 g of H2C2O4‚2H2O, 0.110 g of KFe(C2O4)2,0.200 g of phen, and 15 g of H2O (approximate molar compositionof 1GeO2:2H2C2O4:2/3KFe(C2O4)2:2phen). Yield 58.1% based onKFe(C2O4)2.

Calculated elemental composition (based on single-crystal datafor C42H24N6O12FeGe, MW 933.11; %): C 54.06, N 9.01, H 2.59.Found (%): C 53.70, N 8.76, H 2.49. TGA data (weight lossesinside parentheses): 277-353°C (-59.0%); 353-598°C (-21.0%).

Selected FT-IR and Raman (inside parentheses and in italics) data(in cm-1): ν(C-H, aromatic)) 3076w, (3076); ν(uncoordinatedcarbonyl groups)) 1734s, (1763); νasym(-CO2

-) ) 1671m, 1631w,1577w, (1632, 1602, 1580); ν(C-C, skeletal vibrations)) 1512w,1494w, (1513, 1454); δ(C-H) ) 1425s, (1431); νsym(-CO2

-) )1425s, 1363w, 1328s, (1431, 1345, 1304); ν(C-N, heteroaromaticamines)) 1328s, (1304); ν(C-O) ) 1227s, 1197m, 1140w, (1208,1142, 1105); ν(C-C skeletal stretching mode)) 1096w, 1054w,(1055); ν(C-H) ) 987w, (911); ν(C-C and Ge-O) ) 892m, 842s,819s, (877); δ(CO2

-) ) 771w, 721s, (739); γ(C-H) ) 645w, 595w,532w, (646); ν(M-N) andF(CO2

-) ) 470m, (439).Synthesis of [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b). The syn-

thetic procedure used to isolate this hydrated polymorph of [Fe-(phen)3][Ge(C2O4)3] is identical to that described for1a but usinginstead (NH4)2Fe(SO4)2‚6H2O as the Fe2+ source. The reactionmixture contained 0.050 g of GeO2, 0.180 g of H2C2O4‚2H2O,0.130 g of (NH4)2Fe(SO4)2‚6H2O, 0.200 g of phen, and 15 g ofH2O (approximate molar composition of 1GeO2:3H2C2O4:2/3(NH4)2-Fe(SO4)2‚6H2O:2phen). Yield 53.5% based on (NH4)2Fe(SO4)2‚6H2O.

Calculated elemental composition (based on single-crystal datafor C42H24.40N6O12.20FeGe, MW 936.72; %): C 53.85, N 8.97, H2.63. Found (%): C 53.12, N 8.68, H 2.64. TGA data (weight lossesinside parentheses): 30-268°C (-0.8%); 268-342°C (-59.8%);342-599 °C (-18.8%). Selected FT-IR and Raman (insideparentheses and in italics) data (in cm-1): ν(C-H, aromatic))3071m, (3071); ν(uncoordinated carbonyl groups)) 1740s, (1765,1727); νasym(-CO2

-) ) 1672s, 1614s, (1630, 1600, 1580);ν(C-C, skeletal vibrations)) 1517m, 1494w, (1513, 1453);δ(C-H) ) 1424s, (1427); νsym(-CO2

-) ) 1424s, 1358m, 1313s,(1427, 1341, 1299); ν(C-N, heteroaromatic amines)) 1313s,(1299); ν(C-O) ) 1218m, 1186w, 1141w, (1206, 1141); ν(C-Cskeletal stretching mode)) 1105w, (1106, 1056); ν(C-C and Ge-O) ) 893m, 849m, 817s, (875); δ(CO2

-) ) 725s, (741); γ(C-H)) 646w, 596w, 530w, (647, 596); ν(M-N) andF(CO2

-) ) 470m,420w, (437).

Synthesis of [Ni(phen)3][Ge(C2O4)3] (3). The synthetic proce-dure used to isolate [Ni(phen)3][Ge(C2O4)3] is identical to thatdescribed for1a but using instead NiC4H6O4‚4H2O as the Ni2+

source. The reaction mixture contained 0.050 g of GeO2, 0.180 gof H2C2O4‚2H2O, 0.080 g of NiC4H6O4‚4H2O, 0.200 g of phen,and 15 g of H2O (approximate molar composition of 1GeO2:3H2C2O4:2/3NiC4H6O4:2phen). Yield 53.5% based on NiC4H6O4‚4H2O.

Calculated elemental composition (based on single-crystal datafor C42H24N6O12NiGe, MW 935.97; %): C 53.90, N 8.98, H 2.58.Found (%): C 52.98, N 9.01, H 2.55. TGA data (weight lossesinside parentheses): 280-374°C (-44.9%); 374-599°C (-34.5%).Selected FT-IR and Raman (inside parentheses and in italics) data(in cm-1): ν(C-H, aromatic)) 3073w, (3079); ν(uncoordinatedcarbonyl groups)) 1737s, (1759, 1721); νasym(-CO2

-) ) 1676s,1627m, 1588w, (1627, 1611, 1588); ν(C-C, skeletal vibrations)) 1518m, 1497w, (1517, 1461); δ(C-H) ) 1428s, (1423);νsym(-CO2

-) ) 1428s, 1362s, 1330s, (1423, 1362, 1345, 1322,1311); ν(C-N, heteroaromatic amines)) 1330s, (1322, 1311);ν(C-O) ) 1226m, 1198w, 1146w, (1258, 1206, 1146); ν(C-Cskeletal stretching mode)) 1105w, (1056); ν(C-H) ) 992w, (905);ν(C-C and Ge-O) ) 893w, 845m, 819s, (872); δ(CO2

-) ) 775w,725s, (733); γ(C-H) ) 644w, 595w, (597, 560); ν(M-N) andF(CO2

-) ) 470m, 426w, (514, 485, 426).Synthesis of [Co(phen)3][Ge(C2O4)3] (4). The synthetic proce-

dure used to isolate [Co(phen)3][Ge(C2O4)3] as a microcrystallinelight-yellow powder is identical to that described for1a but using

Shi et al.

6504 Inorganic Chemistry, Vol. 46, No. 16, 2007

instead CoC4H6O4‚4H2O as the Co2+ source. The reaction mixturecontained 0.050 g of GeO2, 0.180 g of H2C2O4‚2H2O, 0.080 g ofCoC4H6O4‚4H2O, 0.200 g of phen, and 15 g of H2O (approximatemolar composition of 1GeO2:3H2C2O4:2/3CoC4H6O4:2phen). Yield83.1% based on CoC4H6O4‚4H2O.

Calculated elemental composition (for C42H24N6O12CoGe, MW936.21; %): C 53.88, N 8.98, H 2.58. Found (%): C 52.00, N 8.63,H 2.54. TGA data (weight losses inside parentheses): 272-360°C(-46.7%); 360-598 °C (-33.3%). Selected FT-IR and Raman

(inside parentheses and in italics) data (in cm-1): ν(C-H, aromatic)) 3061w, 2925w, (3081); ν(uncoordinated carbonyl groups))1735s, (1763, 1721); νasym(-CO2

-) ) 1672m, 1624w, 1605w,1583w, (1626, 1604, 1586); ν(C-C, skeletal vibrations)) 1517m,1496w, (1517, 1453); δ(C-H) ) 1426s, (1422); νsym(-CO2

-) )1426s, 1316s, (1422, 1362, 1345, 1306); ν(C-N, heteroaromaticamines)) 1316s, (1306); ν(C-O) ) 1227m, 1197w, 1187w,1141w, (1259, 1145); ν(C-C skeletal stretching mode)) 1104w,(1054); ν(C-H) ) 992w, 952w, (901); ν(C-C and Ge-O) )

Table 1. Crystal Data Collection and Refinement Details for [M(phen)3][Ge(C2O4)3]‚xH2O [where M2+ ) Cu2+ (1a and1b), Fe2+ (2a and2b), Ni2+

(3); x ) 0.2 for 2b] and [MGe(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)]

1a 1b 2a 2b

formula C42H24N6O12CuGe C42H24N6O12CuGe C42H24N6O12FeGe C42H24.40N6O12.20FeGemol wt 940.80 940.80 933.11 936.72cryst description blue-green prisms blue-green prisms red needles red needlescryst size/mm 0.28× 0.16× 0.15 0.16× 0.15× 0.13 0.32× 0.12× 0.10 0.30× 0.07× 0.02temp/K 100(2) 150(2) 150(2) 150(2)instrument Smart 1000 Bruker X8 Bruker X8 Bruker X8cryst syst monoclinic monoclinic monoclinic triclinicspace group P21/n P21/c P21/n P1ha/Å 9.4730(19) 14.1076(9) 9.3425(5) 11.3137(5)b/Å 20.528(4) 12.9140(8) 20.6117(9) 12.0536(5)c/Å 19.029(4) 20.8073(13) 19.1881(9) 16.0827(11)R/deg 90 90 90 109.059(4)â/deg 96.19(3) 97.982(3) 95.410(2) 94.664(4)γ/deg 90 90 90 111.536vol./Å3 3678.90(13) 3754.1(4) 3678.5 1877.10Z 4 4 4 2Fcalcd/g cm-3 1.699 1.665 1.685 1.657F(000) 1900 1900 1888 948µ/mm-1 1.475 1.445 1.291 1.266θ range/deg 3.68 - 28.40 1.98-25.12 1.45-30.21 3.59-29.13index ranges -12 e h e 12 -15 e h e 16 -13 e h e 9 -15 e h e 15

-27 e k e 27 -15 e k e 15 -29 e k e 28 -16 e k e 16-25 e l e 24 -24 e l e 24 -26 e l e 26 -22 e l e 22

reflns collected 65 748 66 242 75 853 32 834independent reflns 9202 (Rint ) 0.0797) 6659 (Rint ) 0.0699) 10399 (Rint ) 0.0400) 9906 (Rint ) 0.0646)final R indices [I > 2σ(I)] R1 ) 0.0386 R1 ) 0.0309 R1 ) 0.0335 R1 ) 0.0418

wR2 ) 0.0721 wR2 ) 0.0672 wR2 ) 0.0793 wR2 ) 0.0826final R indices (all data) R1 ) 0.0755 R1 ) 0.0458 R1 ) 0.0546 R1 ) 0.0860

wR2 ) 0.0850 wR2 ) 0.0744 wR2 ) 0.0896 wR2 ) 0.0981largest diff. peak and hole/e Å3 0.487 and-0.489 0.389 and-0.452 0.408 and-0.634 0.691 and-0.717

3 5 6

formula C42H24N6O12NiGe C28H18N4O10CdGe C28H18N4O10CuGemol wt 935.97 755.45 706.59cryst description pink prisms colorless prisms green prismscryst size/mm 0.12× 0.05× 0.05 0.20× 0.12× 0.08 0.31× 0.20× 0.18temp/K 110(2) 150(2) 100(2)instrument Kappa FR591 2000 Bruker X8 Smart 1000cryst syst monoclinic monoclinic orthorhombicspace group P21/n C2/c Pnnaa/Å 9.4060(19) 12.7304(2) 15.250(3)b/Å 20.647(4) 17.0619(3) 12.032(2)c/Å 19.022(4) 12.1242(2) 13.582(3)R/deg 90 90 90â/deg 95.09(3) 100.729(1) 90γ/deg 90 90 90vol./Å3 3679.6(13) 2587.40(7) 2492.1(9)Z 4 8 4Fcalcd/g cm-3 1.690 1.939 1.883F(000) 1896 1496 1420µ/mm-1 2.329 2.056 2.134θ range/deg 3.83 - 27.52 3.70 - 27.48 3.70 - 26.39index ranges -9 e h e 9 -16 e h e 16 -19 e h e 15

0 e k e 21 -22 e k e 22 -15 e k e 150 e l e 20 -15 e l e 15 -16 e l e 16

reflns collected 21 054 41 597 21 786independent reflns 4523 (Rint ) 0.0531) 2956 (Rint ) 0.0273) 2557 (Rint ) 0.0975)final R indices [I> 2σ(I)] R1 ) 0.0522 R1 ) 0.0153 R1 ) 0.1050

wR2 ) 0.1382 wR2 ) 0.0392 wR2 ) 0.2622final R indices (all data) R1 ) 0.0531 R1 ) 0.0176 R1 ) 0.1387

wR2 ) 0.1397 wR2 ) 0.0401 wR2 ) 0.2798largest diff. peak and hole/e Å3 0.667 and-0.771 0.361 and-0.247 0.901 and-0.999



892w, 867w, 845m, 819s, (869); δ(CO2-) ) 772w, 725s, (733);

γ(C-H) ) 644w, 602w, (640, 598, 558); ν(M-N) andF(CO2-)

) 470m, 425w, (425).Synthesis of [CdGe(phen)2(µ2-OH)2(C2O4)2] (5). The synthetic

procedure used to isolate [CdGe(phen)2(µ2-OH)2(C2O4)2] as acolorless single-crystalline phase is identical to that described for1a but using instead CdC4H6O4‚2H2O as the Cd2+ source. Thereaction mixture contained 0.100 g of GeO2, 0.360 g of H2C2O4‚H2O, 0.080 g of CdC4H6O4‚2H2O, 0.200 g of phen, and 15 g ofH2O (approximate molar composition of 1GeO2:3H2C2O4:1/3CdC4H6O4‚2H2O:1phen). Yield 88.2% based on CdC4H6O4.

Calculated elemental composition (for C28H18N4O10CdGe, MW755.45, %): C 44.52, N 7.42, H 2.40. Found (%): C 43.78, N7.29, H 2.71. TGA data (weight losses inside parentheses): 30-260°C (-0.6%); 260-343°C (-36.4%); 343-598°C (-29.1%).Selected FT-IR and Raman (inside parentheses and in italics) data(in cm-1): ν(O-H as bridging ligand)) 3321m; νasym(C-H,aromatic rings)) 3074w, (3080, 3052); ν(uncoordinated carbonylgroups)) 1723s;νasym(-CO2

-) ) 1680s, 1621m, 1597m, (1606);ν(C-C, heteroaromatic amines)) 1517m, (1452); δ(C-H) )1428s, (1412); νsym(-CO2

-) ) 1428s, 1359s, (1412, 1375, 1345,1305); ν(C-N, heteroaromatic amines)) 1359s; (1345, 1305);ν(C-O) ) 1246m, 1225m, 1138w, (1257, 1196, 1156); ν(C-Cskeletal stretching mode)) 1100w, (1109); ν(C-H) ) 1053w,(1055); ν(C-C and Ge-O) ) 894w, 853s, 808m, (865); δ(CO2

-)) 773w, 726s, (728, 711); γ(C-H) ) 642m, 597m, (583, 556);ν(M-N) andF(CO2

-) ) 476m, 420w, (422).Synthesis of [CuGe(phen)2(µ2-OH)2(C2O4)2] (6). [CuGe(phen)2-

(µ2-OH)2(C2O4)2] was initially isolated from the reaction vials of1aas a minor impurity. The pure phase was isolated using the samesynthetic procedure with a reaction mixture composed of 0.050 gof GeO2, 0.120 g of H2C2O4‚H2O, 0.100 g of CuC4H6O4‚H2O,0.200 g of phen, and 15 g of H2O (approximate molar compositionof 1GeO2:2H2C2O4:1CuC4H6O4:2phen). Yield 70.8% based onCuC4H6O4‚H2O.

Calculated elemental composition (for C28H18N4O10CuGe, MW706.59; %): C 47.60, N 7.93, H 2.57. Found (%): C 47.96,N 7.90, H 2.55. TGA data (weight losses inside parentheses):105-197 °C (-0.5%); 197-342 °C (-31.6%); 342-599 °C(-42.4%). Selected FT-IR and Raman (inside parentheses and initalics) data (in cm-1): ν(O-H as bridging ligand)) 3396m;νasym(C-H, aromatic rings)) 3086w, (3078); ν(uncoordinatedcarbonyl groups)) 1719s;νasym(-CO2

-) ) 1660s, 1597s, (1607);ν(C-C, heteroaromatic amines)) 1519m, (1457); δ(C-H) )1428s, (1429); νsym(-CO2

-) ) 1428s, 1363s, (1429, 1310);ν(C-N, heteroaromatic amines)) 1363s; (1310); ν(C-O) )1296m, 1248m, 1145w;ν(C-C skeletal stretching mode)) 1107w,(1050); ν(C-H) ) 1034w; ν(C-C and Ge-O) ) 854m, 808m;

δ(CO2-) ) 724s, (736); γ(C-H) ) 647w, 574w, (560); ν(M-N)

andF(CO2- out-of-plane)) 483m, 429w, (432).

Single-Crystal X-ray Diffraction. Crystals of compounds[M(phen)3][Ge(C2O4)3]‚xH2O [where M2+ ) Cu2+ (1aand1b), Fe2+

(2a and2b), Ni2+ (3); x ) 0.2 for 2b] and [MGe(phen)2(µ2-OH)2-(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)] suitable for single-crystal X-ray diffraction analysis were manually harvested fromthe reaction vials and mounted on glass fibers using FOMBLIN Yperfluoropolyether vacuum oil (LVAC 25/6) purchased fromAldrich.45 Data were collected in Nonius-based Kappa Brukerdiffractrometers equipped with charge-coupled device (CCD) areadetectors and Mo KR (λ ) 0.7107 Å) or Cu KR (λ ) 1.54180 Å)(for 3) radiation. Data were corrected for Lorenztian and polarizationeffects. Absorption corrections were applied using the multiscansemiempirical method implemented in SADABS.46 Structures weresolved using the direct methods of SHELXS-97,47 whichallowed immediate location of the heaviest atoms. The re-maining non-hydrogen atoms were located from differenceFourier maps calculated from successive full-matrix least-squaresrefinement cycles onF2 using SHELXL-97.48 All non-hydrogenatoms were successfully refined using anisotropic displacementparameters.

Hydrogen atoms bound to carbon were located at their idealizedpositions by employing theHFIX 43 instruction in SHELXL-9748

and included in subsequent refinement cycles in riding motionapproximation with isotropic thermal displacement parameters (Uiso)fixed at 1.2Ueq of the carbon atom to which they were attached. Incompounds5 and 6 the hydrogen atoms associated with theµ2-bridging hydroxyl groups were markedly visible in the lastdifference Fourier maps synthesis. These atoms have been includedin the final structural models with the O-H distances restrained to0.95(1) Å in order to ensure a chemically reasonable geometry forthese moieties, and withUiso fixed at 1.5Ueq of the parent oxygenatom.

In compound2b a partially occupied water molecule of crystal-lization [O(1W)] was directly located from difference Fourier mapsand refined using an isotropic displacement parameter and a fixedpartial site occupancy of 20% (determined previously by unre-strained refinement of this variable). Even though hydrogen atomsbelonging to this chemical moiety could not be directly locatedfrom difference Fourier maps and no attempt was made to placethese in approximate calculated positions, they have been includedin the empirical formula of the compound. As mentioned in theprevious section, crystals of6 were obtained as a minor phase inthe synthesis of1a. Crystals systematically showed poor qualityassociated with diffuse scattering at high angle (therefore, the highRint; see Table 1).

Information concerning the crystallographic data collection andstructure refinement are collected in Table 1. Selected bond lengthsand angles for compounds1 to 3 are summarized in Tables 2 and3, respectively, while for compounds5 and6 they are collected inTable 9. Geometrical details on the weak C-H‚‚‚O hydrogen-bonding interactions interconnecting cationic [M(phen)3]2+ andanionic [Ge(C2O4)3]2- moieties in compounds1-3 are collected

(45) Kottke, T.; Stalke, D.J. Appl. Crystallogr.1993, 26, 615-619.(46) Sheldrick, G. M.SADABSV.2.01, Bruker/Siemens Area Detector

Absorption Correction Program; Bruker AXS: Madison, WI, 1998.(47) Sheldrick, G. M.SHELXS-97, Program for Crystal Structure Solution;

University of Gottingen: Gottingen, 1997.(48) Sheldrick, G. M.SHELXL-97, Program for Crystal Structure Refine-

ment;University of Gottingen: Gottingen, 1997.

Table 2. Selected Bond Lengths (Å) for the Octahedral{MN6} and{GeO6} Coordination Environments Present in Compounds1-3 (M2+ )Cu2+, Fe2+, or Ni2+)

1a (Cu2+) 1b (Cu2+) 2a (Fe2+) 2b (Fe2+) 3 (Ni2+)

M(1)-N(1) 2.049(2) 2.374(2) 1.992(2) 1.974(2) 2.091(3)M(1)-N(2) 2.025(2) 2.031(2) 1.974(2) 1.986(2) 2.081(3)M(1)-N(3) 2.316(2) 2.021(2) 1.984(2) 1.985(2) 2.088(3)M(1)-N(4) 2.059(2) 2.317(2) 1.978(2) 1.985(2) 2.076(3)M(1)-N(5) 2.042(2) 2.048(2) 1.990(2) 2.002(2) 2.097(3)M(1)-N(6) 2.275(2) 2.056(2) 1.978(1) 1.972(2) 2.085(3)Ge(1)-O(1) 1.883(2) 1.889(2) 1.891(1) 1.897(2) 1.865(2)Ge(1)-O(3) 1.886(2) 1.872(2) 1.892(1) 1.894(2) 1.880(2)Ge(1)-O(5) 1.875(2) 1.870(2) 1.888 (1) 1.893(2) 1.871(2)Ge(1)-O(7) 1.876(2) 1.879(2) 1.878(1) 1.890(2) 1.879(2)Ge(1)-O(9) 1.876(2) 1.895(2) 1.884(1) 1.881(2) 1.886(3)Ge(1)-O(11) 1.870(2) 1.888(2) 1.878(1) 1.890(2) 1.881(2)

Shi et al.


in Tables 4-8. Schematic drawings for all structures have beenprepared using Crystal Diamond49 and the X-seed softwareplatform.50,51

Crystallographic data (excluding structure factors) for thestructures reported in this paper have been deposited with theCambridge Crystallographic Data Centre (CCDC) as supplementarypublication numbers: CCDC-627717 to-627721 (compounds1-3), -628767 and-628768 (compounds5 and6, respectively).Copies of the data can be obtained free of charge on application toCCDC, 12 Union Road, Cambridge CB2 2EZ, U.K. [FAX: (+44)1223 336033; e-mail: [email protected]].

Powder X-ray Diffraction. PXRD data of [Co(phen)3][Ge-(C2O4)3] (4) were collected at ambient temperature on a X’PertMPD Philips diffractometer (Cu KR X-radiation,λ ) 1.54060 Å)equipped with a X’Celerator detector, a curved graphite-mono-chromated radiation, and a flat-plate sample holder in a Bragg-Brentano para-focusing optics configuration (40 kV, 50 mA).Intensity data were collected in continuous scanning mode in therange ca. 4e 2θ° e 55.

The PXRD pattern was indexed with the routines provided withthe program DICVOL0452 using the first 20 well-resolved reflec-

(49) Brandenburg, K.DIAMOND, Version 3.1d; Crystal Impact GbR:Bonn, Germany, 2006.

(50) Barbour, L. J.J. Supramol. Chem.2001, 1, 189-191.(51) Atwood, J. L.; Barbour, L. J.Cryst. Growth Des.2003, 3, 3-8. (52) Boultif, A.; Louer, D.J. Appl. Crystallogr.2004, 37, 724-731.

Table 3. Octahedral Angles (deg) for{MN6} and{GeO6} Coordination Environments Present in Compounds1-3 (M2+ ) Cu2+, Fe2+, or Ni2+)

1a (Cu2+) 1b (Cu2+) 2a (Fe2+) 2b (Fe2+) 3 (Ni2+)

N(1)-M(1)-N(2) 81.32(9) 75.98(8) 82.58(6) 83.09(9) 80.14(10)N(1)-M(1)-N(3) 99.39(9) 105.32(8) 96.45(6) 93.25(9) 95.43(10)N(1)-M(1)-N(4) 174.52(9) 173.47(8) 177.27(6) 174.41(9) 172.97(10)N(1)-M(1)-N(5) 94.85(9) 89.81(8) 93.83(6) 97.32(9) 91.81(10)N(1)-M(1)-N(6) 91.42(9) 84.19(8) 89.55(6) 91.98(9) 88.78(10)N(2)-M(1)-N(3) 93.74(9) 92.17(9) 92.65(6) 92.12(9) 90.98(10)N(2)-M(1)-N(4) 95.65(9) 98.11(8) 94.93(6) 92.93(9) 94.51(10)N(2)-M(1)-N(5) 171.50(9) 165.61(8) 174.87(6) 177.43(9) 168.24(10)N(2)-M(1)-N(6) 94.49(9) 94.70(9) 93.38(6) 94.83(9) 91.84(10)N(3)-M(1)-N(4) 76.18(9) 77.42(8) 82.51(6) 82.94(9) 80.01(10)N(3)-M(1)-N(5) 94.37(9) 93.83(8) 91.40(6) 90.38(9) 98.36(10)N(3)-M(1)-N(6) 167.28(8) 169.42(9) 172.00(6) 171.75(9) 175.28(10)N(4)-M(1)-N(5) 88.75(9) 95.96(8) 88.72(6) 86.82(9) 94.14(10)N(4)-M(1)-N(6) 93.37(9) 93.63(8) 91.73(6) 92.26(9) 95.99(11)N(5)-M(1)-N(6) 77.95(9) 81.38(9) 82.89(6) 82.63(9) 79.34(10)O(1)-Ge(1)-O(3) 85.83(9) 86.52(8) 85.90(6) 85.64(8) 86.57(10)O(1)-Ge(1)-O(5) 87.10(8) 89.49(8) 87.01(6) 88.12(9) 93.26(10)O(1)-Ge(1)-O(7) 172.12(8) 175.57(8) 172.11(6) 170.87(9) 177.28(10)O(1)-Ge(1)-O(9) 90.29(8) 88.28(8) 90.09(6) 92.15(9) 88.78(11)O(1)-Ge(1)-O(11) 93.86(9) 95.29(8) 94.15(6) 95.06(9) 93.81(11)O(3)-Ge(1)-O(5) 93.72(9) 95.83(8) 93.75(6) 93.89(9) 93.64(10)O(3)-Ge(1)-O(7) 90.45(9) 92.43(8) 90.83(6) 88.05(9) 90.86(10)O(3)-Ge(1)-O(9) 173.86(8) 171.66(8) 173.93(6) 173.83(9) 173.54(10)O(3)-Ge(1)-O(11) 88.92(9) 88.16(8) 89.28(6) 88.82(9) 89.92(10)O(5)-Ge(1)-O(7) 86.21(8) 86.33(8) 86.04(6) 85.72(9) 86.04(10)O(5)-Ge(1)-O(9) 90.83(9) 90.64(8) 90.59(6) 91.79(9) 91.09(10)O(5)-Ge(1)-O(11) 177.25(9) 173.95(8) 176.83(6) 175.97(9) 172.26(10)O(7)-Ge(1)-O(9) 93.97(8) 93.24(8) 93.70(6) 94.77(9) 93.86(10)O(7)-Ge(1)-O(11) 93.01(9) 88.98(8) 92.98(6) 91.40(9) 87.04(10)O(9)-Ge(1)-O(11) 86.59(8) 85.82(8) 86.47(6) 85.63(9) 85.93(10)

Table 4. Geometrical Parameters for the Possible Weak C-H‚‚‚OHydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anionsand [Cu(phen)3]2+ Cations in the Polymorphic Structure of Compound1aa

C-H‚‚‚O dC‚‚‚O (Å) ∠(CHO) (deg)

C(7)-H(7)‚‚‚O(6)i 3.229(4) 125C(8)-H(8)‚‚‚O(8)i 3.245(4) 132C(14)-H(14)‚‚‚O(10)ii 3.192(4) 115C(18)-H(18)‚‚‚O(4) 2.997(3) 109C(20)-H(20)‚‚‚O(12)iii 3.296(4) 138C(21)-H(21)‚‚‚O(11)iii 3.502(4) 153C(28)-H(28)‚‚‚O(1)iv 3.147(3) 126C(29)-H(29)‚‚‚O(2) 3.266(4) 117C(30)-H(30)‚‚‚O(2) 3.163(4) 129C(33)-H(33)‚‚‚O(4)i 3.375(4) 141C(38)-H(38)‚‚‚O(6)v 3.125(4) 130C(41)-H(41)‚‚‚O(10)vi 3.515(4) 150

a Symmetry transformations used to generate equivalent atoms: (i) 1/2- x, -1/2 + y, 1.5 - z; (ii) -1.5 + x, 1/2 - y, -1/2 + z; (iii) -x, -y, 2- z; (iv) 1 - x, -y, 2 - z; (v) 1.5 - x, -1/2 + y, 1.5 -z; (vi) -1/2 + x,1/2 - y, -1/2 + z.

Table 5. Geometrical Parameters for the Possible Weak C-H‚‚‚OHydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anionsand [Cu(phen)3]2+ Cations in the Polymorphic Structure of Compound1ba


C(7)-H(7)‚‚‚O(1)i 3.339(3) 143C(9)-H(9)‚‚‚O(8)ii 3.393(3) 161C(14)-H(14)‚‚‚O(9)iii 3.577(3) 166C(15)-H(15)‚‚‚O(6)ii 3.081(3) 116C(15)-H(15)‚‚‚O(10)iii 3.400(4) 131C(18)-H(18)‚‚‚O(7)iv 3.235(3) 115C(19)-H(19)‚‚‚O(10)i 3.158(3) 115C(20)-H(20)‚‚‚O(10)i 3.182(3) 111C(21)-H(21)‚‚‚O(10)v 3.244(3) 137C(27)-H(27)‚‚‚O(7)vi 3.362(3) 135C(31)-H(31)‚‚‚O(12)vii 3.360(4) 142C(40)-H(40)‚‚‚O(2)viii 3.117(4) 130C(41)-H(41)‚‚‚O(2)vi 3.269(4) 116C(42)-H(42)‚‚‚O(12)ix 3.273(3) 143

a Symmetry transformations used to generate equivalent atoms: (i) 1-x, 1/2 + y, 1/2 - z; (ii) 1 - x, 1 - y, -z; (iii) -1 + x, 1/2 - y, -1/2 +z; (iv) 1 - x, -y, -z; (v) -1 + x, y, z; (vi) 1 - x, -1/2 + y, 1/2 - z;(vii) 1 - x, 1/2+ y, 1/2- z; (viii) 1 - x, 1/2+ y, 1/2- z; (ix) 1 - x, -y,-z.



tions (located using the derivative-based peak search algorithmprovided with Fullprof.2k)53,54 and a fixed absolute error on eachline of 0.03° 2θ. Initial unit cell metrics were obtained withreasonable figures-of-merit: M(20)55 ) 12.5 and F(20)56 ) 30.2;zero shift of-0.0436°. Analysis of the systematic absences usingCHECKCELL57 unambiguously confirmed space groupP21/n. A

Le Bail whole-powder-diffraction-pattern profile fitting58 (see FigureS1 in the Supporting Information) was performed with theFullProf.2k software package,53,54employing a typical pseudo-Voigtpeak-shape function, and in the last stages of the fitting processthe unit cell parameters and typical profile parameters, such as scalefactor, zero shift, Caglioti function values, and two asymmetryparameters were allowed to refine freely. Fixed background pointswere employed. The refined unit cell parameters converged toa )19.204(2) Å,b ) 20.839(2) Å,c ) 9.511(1) Å, andâ ) 95.066-(6)° (RBragg ) 1.06% andø2 ) 3.79)

Results and Discussion

A series of highly crystalline heterodimetallic complexescomposed of tris(oxalato-O,O′)germanate anions and cationiccomplexes of transition metals (M) coordinated to 1,10′-phenanthroline (phen) residues have been isolated using mildhydrothermal synthesis, from reaction mixtures containinggermanium(IV) oxide, oxalic acid, phen, and various M salts(see Experimental Section for details). Compounds have beenformulated as [M(phen)3][Ge(C2O4)3]‚xH2O [where M2+ )Cu2+ (1a and1b), Fe2+ (2a and2b), Ni2+ (3), and Co2+ (4);x ) 0.2 for compound2b] on the basis of single-crystal orpowder X-ray diffraction studies and elemental analysis. EDSstudies provided information on (1) the presence of Ge andthe metallic centers on individual crystals of each compoundand (2) the ratios of Ge:M, typically 1:1.

Crystalline phases were directly isolated from the autoclavecontents in generous yields and usually as large singlecrystals, except for4 which could only be synthesized as amicrocrystalline powder (Figure 1). Phase purity and ho-mogeneity of the bulk samples of1b and 2-4 have beenconfirmed by comparing the experimental powder X-raydiffraction patterns with simulations based on single-crystaldata. Compound1awas systematically isolated with a smallamount of compound6 which could not be eliminated eitherat the synthesis stage or after. Nevertheless, according tothe CHN elemental composition of several representativebulk samples of1a we determined that the amount of thisimpurity was quite small. However, during our syntheticattempts to eliminate this second-phase (by varying thecomposition of the reaction mixture used to isolate1a) asecond polymorphic (and pure) phase was isolated for aslightly higher amount of phen in the reaction mixture (seeExperimental Section for details on the synthetic procedures).

It is also of considerable interest to mention that for Fe2+

two structures could also be isolated, [Fe(phen)3][Ge(C2O4)3](2a) and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b), with the latter

(53) Rodriguez-Carvajal, J.FULLPROF-A Program for RietVeld Refinementand Pattern Matching Analysis,Abstract of the Satellite Meeting onPowder Diffraction of the XV Congress of the IUCR, Toulouse,France, 1990; p 127.

(54) Roisnel, T.; Rodriguez-Carvajal, J.WinPLOTR [June 2005]-A Win-dows Tool for Powder Diffraction Pattern Analysis.Materials ScienceForum, Proceedings of the Seventh European Powder DiffractionConference (EPDIC 7); Delhez, R., Mittenmeijer, E. J., Eds.; 2000,pp 118-123.

(55) Boultif, A.; Louer, D.J. Appl. Crystallogr.1991, 24, 987-993.(56) Louer, D. In Automatic Indexing: Procedures and Applications,

Accuracy in Powder Diffraction II; Gaithersburg, MD, 1992; pp 92-104.

(57) Laugier, J.; Bochu, B.CHECKCELL-A Software Performing AutomaticCell/Space Group Determination,Collaborative Computational ProjectNumber 14 (CCP14), Laboratoire des Mate´riaux et du Ge´nie Physiquede l’Ecole Supe´rieure de Physique de Grenoble (INPG), France, 2000.

(58) LeBail, A.; Duroy, H.; Fourquet, J. L.Mater. Res. Bull.1988, 23,447-452.

Table 6. Geometrical Parameters for the Possible Weak C-H‚‚‚OHydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anionsand [Fe(phen)3]2+ Cations in2aa


C(7)-H(7)‚‚‚O(6)i 3.187(2) 124C(8)-H(8)‚‚‚O(8)i 3.294(4) 135C(18)-H(18)‚‚‚O(4) 3.028(2) 105C(20)-H(20)‚‚‚O(12)ii 3.369(3) 128C(21)-H(21)‚‚‚O(11)ii 3.551(3) 163C(28)-H(28)‚‚‚O(2)iii 3.146(2) 126C(30)-H(30)‚‚‚O(2) 3.186(2) 108C(33)-H(33)‚‚‚O(4)i 3.388(3) 137C(38)-H(38)‚‚‚O(6)iv 3.157(3) 125C(39)-H(39)‚‚‚O(6)iv 3.246(2) 118C(41)-H(41)‚‚‚O(10)v 3.564(3) 156

a Symmetry transformations used to generate equivalent atoms: (i) 1.5- x, -1/2 + y, 1.5 - z; (ii) 2 - x, -y, 1 - z; (iii) 1 - x, -y, 1 - z;(iv) 1/2 - x, -1/2 + y, 1.5 - z; (v) 1/2 + x, 1/2-y, 1/2 + z.

Table 7. Geometrical Parameters for the Possible Weak C-H‚‚‚OHydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anionsand [Fe(phen)3]2+ Cations in the Solvate Structure of Compound2ba


C(14)-H(14)‚‚‚O(4)i 3.362(4) 131C(15)-H(15)‚‚‚O(5)i 3.417(4) 160C(16)-H(16)‚‚‚O(6)ii 3.513(4) 162C(20)-H(20)‚‚‚O(2)iii 3.335(5) 133C(30)-H(30)‚‚‚O(7)iv 3.196(4) 127C(31)-H(31)‚‚‚O(9)v 3.205(5) 142C(32)-H(32)‚‚‚O(10)vi 3.225(4) 120C(39)-H(39)‚‚‚O(2) 3.110(3) 122C(40)-H(40)‚‚‚O(4)vii 3.117(3) 120C(41)-H(41)‚‚‚O(4)vii 3.181(4) 117C(42)-H(42)‚‚‚O(3)iv 3.037(3) 102C(42)-H(42)‚‚‚O(4)iv 3.468(3) 146

a Symmetry transformations used to generate equivalent atoms: (i) 2-x, 2 - y, z; (ii) 2 + x, 1 + y, z; (iii) 2 - x, 2 - y, 1 - z; (iv) 1 + x, 1 +y, z; (v) 1 + x, y, z; (vi) 1 - x, 2 - y, 1 - z; (vii) 1 - x, 2 - y, z.

Table 8. Geometrical Parameters for the Possible Weak C-H‚‚‚OHydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anionsand [Ni(phen)3]2+ Cations in3a


C(9)-H(9)‚‚‚O(10)i 3.358(4) 137C(14)-H(14)‚‚‚O(8)ii 3.129(4) 128C(19)-H(19)‚‚‚O(8)i 3.211(4) 127C(20)-H(20)‚‚‚O(6)i 3.295(4) 132C(26)-H(26)‚‚‚O(4)iii 3.183(5) 115C(30)-H(30)‚‚‚O(10)iv 3.045(5) 112C(32)-H(32)‚‚‚O(2)v 3.313(5) 133C(33)-H(33)‚‚‚O(1)v 3.510(5) 158C(40)-H(40)‚‚‚O(11)v 3.148(5) 126C(40)-H(40)‚‚‚O(12)vi 3.650(5) 173C(42)-H(42)‚‚‚O(12)iv 3.159(5) 131

a Symmetry transformations used to generate equivalent atoms: (i) 1.5- x, -1/2 + y, 1.5- z; (ii) 1/2 - x, -1/2 + y, 1.5- z; (iii) 1/2 - x, 1/2- y, -1/2 - z; (iv) -1 + x, y, -1 + z; (v) 2 - x, -y, 1-z; (vi) 1 - x, -y,1-z.

Shi et al.


being a solvate of the former and typically obtained for aslightly higher concentration of oxalic acid in the reactionmixture (see Experimental Section). This extra partiallyoccupied water molecule of crystallization induces long-rangestructural modifications in the crystal packing, namely, areduction in crystal symmetry from the monoclinic to thetriclinic crystal systems (see structural details in the followingparagraphs).

Structural Details of the [Ge(C2O4)3]2- Anion. Thechemical moiety common to structures1-4 is the divalenttris(oxalate-O,O′)germanate anion, [Ge(C2O4)3]2- (Figure 2and Scheme 1). A search in the literature and in the CSD39,40

reveals only a handful of crystallographic reports41-44

describing this anion which, invariably, shows identicalcoordination geometry for all compounds, including thosereported herein. The Ge4+ center appears coordinated to threeoxalate anions (coordinated via a typicalanti,anti-chelatebidentate fashion), describing a slightly distorted{GeO6}octahedral coordination fashion as depicted in Figure 2. TheGe-O bonds (for all five crystal structure determinationsreported here) are found in the 1.865(2)-1.897(2) Å (Table2), while thecis andtransO-Ge-O octahedral angles areinstead in the 85.64(8)-95.83(8)° and 170.87(9)-177.28-(10)° ranges, respectively (Table 3). These values are in goodagreement with those described for the aforementionedrelated compounds available in the literature, which showan average Ge-O bond length of ca. 1.88 Å plus average

cis (or chelate bite angle) andtrans O-Ge-O octahedralangles of 85.7° and 173.6°, respectively.41-44

Crystal Structure Description of [Cu(phen)3][Ge-(C2O4)3] (1a and 1b).Two crystalline forms of [Cu(phen)3]-[Ge(C2O4)3], 1a and1b, have been isolated from hydrother-mal synthesis (see Experimental Section), crystallizing in theP21/n andP21/c monoclinic space groups, respectively. Forboth crystalline materials the asymmetric unit comprises twodiscrete (and charged) crystallographically independentdivalent residues: one [Cu(phen)3]2+ cation plus one[Ge(C2O4)3]2- anion (Figure 3).

The crystallographically independent Cu2+ centers in1aand1b are coordinated by three phen organic ligands via atypical N,N-chelating coordination fashion, leading to dis-torted{CuN6} octahedral coordination geometries evidencingthe typical Jahn-Teller distortion expected for these d9

metallic centers: while the equatorial Cu-N bond lengthsare found in the 2.021(2)-2.059(2) Å range, the apicalinteractions are much longer and within the 2.275(2)-2.374(2) Å range (Table 2), thus leading to a tetragonaldistortion of the{CuN6} octahedra. The former bond lengthsare well within the expected values, as revealed by a searchin the CSD for structures containing [Cu(phen)3]2+ cations(15 entries; range 2.01-2.34 Å), however, the latter valuesare slightly longer, in particular for1b (see Table 2). Suchabnormal long Cu-N interactions with phen residues canbe rationalized by taking into account intermolecular interac-

Figure 1. SEM images of [M(phen)3][Ge(C2O4)3] crystals with M2+ ) Ni2+ (3) (right) and Co2+ (4) (left).

Table 9. Selected Bond Lengths (Å) and Angles (deg) for the Octahedral{MN4O2} and{GeO6} Coordination Environments Present in Compounds5and6 (M2+ ) Cd2+ or Cu2+)a

bond lengths (Å) bond angles (deg)

5 (Cd2+) 6 (Cu2+) 5 (Cd2+) 6 (Cu2+)

M(1)-N(1) 2.311(1) 1.989(1) N(1)-M(1)-N(2) 72.32(4) 81.4(4)M(1)-N(2) 2.339(1) 2.138(1) N(1)-M(1)-O(5) 88.63(4) 89.2(4)M(1)-O(5) 2.297(1) 2.206(9) N(1)-M(1)-N(1)i 157.40(6) 170.2(6)

N(1)-M(1)-N(2)i 93.03(4) 93.2(4)N(1)-M(1)-O(5)i 110.67(4) 98.9(4)N(2)-M(1)-O(5) 97.08(4) 89.3(3)N(2)-M(1)-N(2)i 100.39(6) 112.7(5)N(2)-M(1)-O(5)i 162.11(4) 158.0(3)O(5)-M(1)-O(5)i 65.81(5) 68.8(4)

Ge(1)-O(1) 1.941(1) 1.951(8) O(1)-Ge(1)-O(3) 83.89(4) 83.8(4)Ge(1)-O(3) 1.899(1) 1.898(8) O(1)-Ge(1)-O(5) 92.18(5) 175.7(4)Ge(1)-O(5) 1.817(1) 1.823(8) O(1)-Ge(1)-O(1)i 89.19(6) 89.2(5)

O(1)-Ge(1)-O(3)i 87.14(4) 87.5(4)O(1)-Ge(1)-O(5)i 175.64(4) 92.4(4)O(3)-Ge(1)-O(5) 97.12(5) 92.2(4)O(3)-Ge(1)-O(3)i 167.40(6) 167.8(5)O(3)-Ge(1)-O(5)i 92.04(5) 96.7(4)O(5)-Ge(1)-O(5)i 86.75(7) 86.3(6)

a Symmetry transformation used to generate equivalent atoms: (i)-x, y, 1.5 - z.



tions, in particular the weak C-H‚‚‚O interactions whichlead to local distortions in order to promote a more effectiveclose packing (see following paragraphs). Structural distor-tions associated with1b are particularly well demonstratedby thecis octahedral angles whose range is the largest of allrelated structures reported herein (see Table 3).

The most remarkable structural feature which differentiates1a and 1b structures concerns the number and type of

intermolecular C-H‚‚‚O weak hydrogen bonds (not shown;Tables 4 and 5 collect some geometrical details of the mostrelevant and chemically feasible interactions) plus interac-tions of the C-H‚‚‚π type and π-π stacking betweenneighboring phen residues belonging to distinct cationicresidues (Figure 4).59 These supramolecular networks of weakintermolecular interactions establish physical connectionsbetween individual moieties and are responsible for com-pletely distinct packing arrangements, as shown in Figure5. Moreover, these interactions are ultimately the main reasonresponsible for the isolation of two distinct crystalline forms.In 1a the [Cu(phen)3]2+ cationic residues pack in chain-likearrangements along the [100] and [001] crystallographicdirections (Figure 4a and 4b). While down the [100] directionadjacent [Cu(phen)3]2+ cations interact only via C-H‚‚‚πcontacts [see Figure 4a;π represents the centroid of theneighboring adjacent aromatic ring; approximate C‚‚‚πdistances: H(19) 3.34 Å, H(20) 3.22 Å, H(40) 3.31 Å, H(41)3.36 Å], along the [001] direction connections betweenneighboring complexes alternate betweenπ-π stacking andC-H···π interactions [C(8)-H(8)‚‚‚π with C‚‚‚π distance of3.22 Å; see Figure 4b]. In1b only one structurally relevantC-H‚‚‚π interaction was observed along the [001] directionof the unit cell [Figure 4c; C(29)sH(29)‚‚‚π with C‚‚‚πaverage distance of 3.20 Å]. Noteworthy is the fact that thiscontact seems to promote the unusually long Cu-N bondsdiscussed above. Indeed, in order to maximize the geometryassociated with this C-H‚‚‚π interaction, one coordinatedphen residue needs to be slightly rotated. This leads, on onehand, to longer bond lengths (because of the structuralrigidity of this organic ligand) and, on the other, to the largecis octahedral angles (see above). It is also of considerableimportance to mention that adjacent phen residues in1b aretoo far apart (average distance of ca. 4.3 Å), thus invalidatingthe occurrence ofπ-π stacking (as also depicted in Figure4c).

Crystal Structure Description of [Fe(phen)3][Ge-(C2O4)3] (2a) and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b).When Fe2+ is included in the reaction mixtures (seeExperimental Section) two pseudo-polymorphic crystallineforms could be isolated with empirical formulas [Fe(phen)3]-[Ge(C2O4)3] and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O for com-pounds2a and 2b, respectively. Pseudo-polymorphism isdefined as crystalline forms of a given compound (host) thatdiffer in the chemical nature or stoichiometry of the includedsolvent molecules (guest) and refers to crystalline forms withsolvent molecules as structurally relevant features of thestructure (isolated lattice sites, lattice channels, or metal-ion-coordinated solvates).60,61

The striking difference between these two compounds isthe presence of one partially occupied (1/5) water moleculeof crystallization in the asymmetric unit of2b, a uniquefeature among the series of compounds reported here. It is

(59) Russell, V.; Scudder, M.; Dance, I.Dalton Trans.2001, 789-799.(60) Robin, A. Y.; Fromm, K. M.Coord. Chem. ReV. 2006, 250, 2127-

2157.(61) Bernstein, J. Organic Solid State Chemistry. InStudies in Organic

Chemistry; Desiraju, G. R., Ed.; Elsevier: Amsterdam, 1987; Vol.32.

Figure 2. Anionic [Ge(C2O4)3]2- fragment common to structures1-4.The represented structure was taken from the structure of complex1b andis represented with thermal ellipsoids drawn at the 50% probability leveland showing the labeling scheme for all atoms. For selected bond lengthsand angles related to this moiety in structures1-3 see Tables 2 and 3,respectively.

Figure 3. Two crystallographic independent chemical moieties, [M(phen)3]2+

and [Ge(C2O4)3]2-, composing the crystal structures of1-3 {from therefined structure of polymorph [Cu(phen)3][Ge(C2O4)3] (1b)} and showingthe labeling scheme for all non-hydrogen atoms. Atoms are drawn as thermalellipsoids at the 50% probability level, and hydrogen atoms have beenomitted for clarity. For selected bond lengths and angles see Tables 2 and3, respectively.

Shi et al.


also of considerable interest to note that this occurrenceseems to be the promoting structural reason for the decreaseof crystal symmetry:2b crystallizes in the triclinicP1h spacegroup, while2a (as for all remaining heterometallic complexstructures) is monoclinic (in this case described in theP21/nspace group) or higher. Disregarding the presence of water,the asymmetric units of2a and2b share many similaritieswith those described for the two previous compounds,comprising two crystallographically independent and chargedions: [Fe(phen)3]2+ and [Ge(C2O4)3]2-. The Fe2+ centersexhibit an almost regular{FeN6} octahedral coordinationenvironment with the Fe-O bond lengths andcis- andtrans-N-Fe-N octahedral angles being found in the 1.972(2)-2.002(2) Å (Table 2) and 82.58(8)-97.32(9)° and 171.75-(9)-177.43(10)° (Table 3) ranges, respectively. These valuesare in agreement with those found in similar structurescontaining [Fe(phen)3]2+ complexes, as revealed by a searchin the CSD and in the literature.

The partially occupied water molecule of crystallization[O(1W)] is strongly hydrogen bonded to two neighboringdivalent [Ge(C2O4)3]2- anionic fragments, establishing aconnection between these two moieties (Figure 6): O(1W)donates its two hydrogen atoms to O(7) and O(10) fromdistinct anions, withdO‚‚‚O of 3.031(2) and 2.881(1) Å,respectively. As also depicted in Figure 6, these bonding

interactions occur in symmetry-related pairs with the twowater molecules being separated by 4.004(2) Å. The motifcan be described by theR4

4(16) graph set notation.62

As for 1a and 1b (see previous subsection), the crystalstructure of these two pseudo-polymorphic compounds isassembled by extensive networks of weak CsH‚‚‚O interac-tions involving the charged species. Chemically (and struc-turally) possible C‚‚‚O intermolecular distances span from3.028(2) to 3.564(3) Å for2a (Table 6) and from 3.037(3)to 3.513(4) Å for2b (Table 7). In the same way as for1a,in 2a intermolecular interactions are composed of both CsH‚‚‚π andπ-π contacts between phen molecules belongingto neighboring [Fe(phen)3]2+ complexes. While along the[100] direction connections are assured by only Cs H‚‚‚πinteractions (as in Figure 4a), parallel to the [001] directionan alternation between CsH‚‚‚π and π-π contacts isregistered (as in Figure 4b).59 In 2b only C-H‚‚‚π interac-tions (running parallel to the [100] crystallographic direction)are structurally relevant as physical connections betweenadjacent cationic residues (Figure 7).

The presence of the extra solvent molecule in2b alsoinduces a completely distinct packing arrangement. While

(62) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N. L.Angew. Chem.,Int. Ed. Engl.1995, 34, 1555-1573.

Figure 4. Close packing of cationic [Cu(phen)3]2+ fragments along the (a) [100] and (b) [001] crystallographic directions of polymorph1a and along the(c) [001] direction for polymorph1b, emphasizing the C-H‚‚‚π andπ-π interactions (dashed lines) interconnecting these moieties. For clarity, only thehydrogen atoms involved in the represented interactions are shown. Geometrical details (approximate C‚‚‚π distances) on structurally relevant C-H‚‚‚πinteractions (π represents the centroid of the aromatic ring): C(19)-H(19)‚‚‚π 3.34 Å; C(20)-H(20)‚‚‚π 3.22 Å, C(40)-H(40)‚‚‚π 3.31 Å,C(41)-H(41)‚‚‚π 3.36 Å; C(8)-H(8)‚‚‚π 3.22 Å; C(29)-H(29)‚‚‚π 3.20 Å.



for 2a the crystal packing is identical to that previouslydescribed for1a (as in Figure 5a), in2b [Fe(phen)3]2+ cationsalternate along the [010] direction of the unit cell with[Ge(C2O4)3]2- anions, almost perfectly aligned in a typicaleclipsed fashion (Figure 8). Interstitial spaces are occupiedby the hydrogen-bonded water molecules of crystallization.

Crystallographic Aspects of [Ni(phen)3][Ge(C2O4)3] (3)and[Co(phen)3][Ge(C2O4)3] (4). [Ni(phen)3][Ge(C2O4)3] (3)crystallizes in the monoclinicP21/n space group, as revealedby single-crystal X-ray diffraction (Table 1), and its molec-ular structure shares striking resemblances with those previ-ously described for compounds1a and 2a (see previoussections for details on the crystal structure). Relevantgeometrical details associated with the Ge4+ and Ni2+

coordination environments of3 are collected in Tables 2and 3.

The compound with Co2+, formulated as [Co(phen)3][Ge-(C2O4)3] (4) on the basis of elemental analysis (and othersupporting techniques), was also found to be isostructural

with 1a and2a from powder X-ray diffraction studies (seedetails in the Experimental Section).

Crystal Structure Description of [MGe(phen)2(µ2-OH)2-(C2O4)2] (where M2+ ) Cd2+ and Cu2+ for 5 and 6). Theneutral hetero-binuclear compounds formulated as [MGe-(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+

(6)] represent, to the best of our knowledge, the firstexamples of binuclear complexes containing a neutral bis-(oxalate-O,O′)germanium fragment, [Ge(C2O4)2], connectedby twoµ2-bridging hydroxyl groups to a cationic [M(phen)2]2+

fragment (Figure 9). Moreover, a search in the literaturereveals that these two isostructural complexes are also thefirst examples of hydroxyl-bridged [M(phen)2]2+ fragments,and only a handful of structures are known to containµ2-oxo bridges involving this fragment.63-75

The neutral bis(oxalate-O,O′) germanium fragment, [Ge-(C2O4)2], shares structural similarities with the [Ge(C2O4)3]2-

complex discussed above and present in structures1-4.However, in5 and6 the Ge4+ center is only coordinated to

(63) Xiao, D. R.; Xu, Y.; Hou, Y.; Wang, E. B.; Wang, S. T.; Li, Y. G.;Xu, L.; Hu, C. W.Eur. J. Inorg. Chem.2004, 1385-1388.

(64) Qi, Y. J.; Wang, Y. H.; Li, H. M.; Cao, M. H.; Hu, C. W.; Wang, E.B.; Hu, N. H.; Jia, H. Q.J. Mol. Struct.2003, 650, 123-129.

(65) Devi, R. N.; Burkholder, E.; Zubieta, J.Inorg. Chim. Acta2003, 348,150-156.

(66) Liu, C. M.; Zhang, D. Q.; Xiong, M.; Dai, M. Q.; Hu, H. M.; Zhu, D.B. J. Coord. Chem.2002, 55, 1327-1335.

(67) Lu, Y.; Wang, E. B.; Yuan, M.; Li, Y. G.; Xu, L.; Hu, C. W.; Hu, N.H.; Jia, H. Q.Solid State Sci.2002, 4, 449-453.

(68) Lu, Y.; Wang, E. B.; Yuan, M.; Li, Y. G.; Hu, C. W.; Hu, N. H.; Jia,H. Q. J. Mol. Struct.2002, 607, 189-194.

(69) Liu, C. M.; Hou, Y. L.; Zhang, J.; Gao, S.Inorg. Chem.2002, 41,140.

(70) Zhang, X. M.; Tong, M. L.; Chen, X. M.Chem. Commun.2000,1817-1818.

(71) Mizutani, M.; Tomosue, S.; Kinoshita, H.; Jitsukawa, K.; Masuda,H.; Einaga, H.Bull. Chem. Soc. Jpn.1999, 72, 981-988.

(72) Xu, J. Q.; Wang, R. Z.; Yang, G. Y.; Xing, Y. H.; Li, D. M.; Bu, W.M.; Ye, L.; Fan, Y. G.; Yang, G. D.; Xing, Y.; Lin, Y. H.; Jia, H. Q.Chem. Commun.1999, 983-984.

(73) Reddy, K. R.; Rajasekharan, M. V.; Arulsamy, N.; Hodgson, D. J.Inorg. Chem.1996, 35, 2283-2286.

(74) Vincent, J. M.; Menage, S.; Latour, J. M.; Bousseksou, A.; Tuchagues,J. P.; Decian, A.; Fontecave, M.Angew. Chem., Int. Ed. Engl.1995,34, 205-207.

(75) Tokii, T.; Ide, K.; Nakashima, M.; Koikawa, M.Chem. Lett.1994,441-444.

Figure 5. Schematic representations of the crystal packing of (a)1a (alongthe [100] direction) and (b)1b (along the [010] direction). Hydrogen atomshave been omitted for clarity.

Figure 6. O-H‚‚‚O hydrogen-bonding interactions (dashed blue lines)involving the partially occupied water molecule of crystallization in pseudo-polymorph2b, [Fe(phen)3][Ge(C2O4)3]‚0.2H2O, interconnecting neighboring[Ge(C2O4)3]2- anionic fragments and leading to formation of aR4

4(16) graphset motif. Geometrical aspects of the represented hydrogen bonds:O(1W)i‚‚‚O(7)iii with dO‚‚‚O of 3.031(2) Å; O(1W)i‚‚‚O(10) with dO‚‚‚O of2.881(1) Å. Symmetry transformations used to generate equivalent atoms:(i) 1 - x, 2 - y, 1 - z; (ii) -1 +x, y, z; (iii) -x, 2 - y, 1 - z.

Shi et al.


two O,O-chelate oxalate anions, with the two remainingvacant positions in the coordination sphere being occupiedby two µ2-bridging hydroxyl groups (Figure 9). The coor-dination environment of Ge4+ centers can thus be envisagedas distorted octahedra,{GeO6}, with the Ge-O bonds beingfound (for the two complexes) between 1.8166(10) and1.951(8) Å while thecis and trans O-Ge-O angles are inthe 83.8(4)-97.12(5)° and 167.40(6)-175.7(4)° ranges,respectively (Table 9). The presence ofµ2-bridging hydroxylgroups induces in the Ge4+ centers octahedral distortionsgreater than those observed for the [Ge(C2O4)3]2- anions(Table 3) with this being essentially attributed to the strongerbonding nature of these chemical moieties. Consequently,the registered Ge-OH bond distances are statistically smaller(below ca. 1.82 Å) than those with oxalate anions (alwaysgreater than ca. 1.90 Å; Table 9), even though they comparewell with the only report in the literature containing a Ge-(OH)-M bridge (d(Ge-OH) of about 1.78 Å) and presentin an open-framework containing germanium clusters.76

Moreover, thetrans effect of theseµ2-OH groups in the{GeO6} octahedra is also markedly present with the oppositeGe-Ooxalatebonds [1.9413(10) and 1.951(8) Å for5 and6,respectively] being the longest among all the structuresreported here.

The M centers exhibit distorted octahedral coordinationgeometries composed by two symmetry-relatedN,N-chelatingphen ligands plus two symmetry-relatedµ2-bridging hydroxylgroups,{MN4O2} (Figure 9): the M-(N,O) bond lengthsare found in the 2.2967(10)-2.3385(12) and 1.989(10)-2.206(9) Å ranges for5 and 6, respectively;cis and transinternal octahedral angles can be found in the 65.81(5)-100.39(6) and 157.40(6)-162.11(4)° (for 5) and in the 68.8-(4)-112.7(5)° and 158.0(3)-170.2(6)° ranges, respectively(see Table 9 for details). Noteworthy is the fact that for6the {CuN4O2} coordination environment is not as signifi-cantly distorted as those registered for1a and 1b, andconsequently the Jahn-Teller distortion is not so markedlyvisible. It is feasible to assume that this smaller tetragonaldistortion for6 seems to arise mainly due to the presence ofthree crystallographically independent Cu-(N,O) bond lengths,which are all statistically distinct as summarized in Table 9.The intermetallic Ge(1)‚‚‚M(1) separations across the hy-droxyl µ2 bridge are 3.2487(3) and 3.1510(27) Å for5 (Cd)and6 (Cu), respectively.

The close packing in the solid state of individual [MGe-(phen)2(µ2-OH)2(C2O4)2] complexes is mediated by a numberof intermolecular interactions, in particular strong and highlydirectional O-H‚‚‚O hydrogen bonds involving anionic [Ge-(µ2-OH)2(C2O4)2]2- fragments belonging to neighboringcomplexes: µ2-bridging hydroxyl groups donate their hy-drogen atoms to neighboring oxalate anions [O(5)sH(5A)‚‚‚O(2)i; for 5, d(O‚‚‚O) ) 2.7699(15) Å with∠(OHO)) 170.3(2)°; for 6, d(O‚‚‚O) ) 2.7791(13) Å with∠(OHO)) 168.0(1)°; symmetry operation (i)-x, -y, 1 - z], leadingto formation of aR2

2(12) graph set motif.62 The reciprocityof these hydrogen-bonding interactions leads to formationof 1D supramolecular tapes,∞

2[MGe(phen)2(µ2-OH)2(C2O4)2],as depicted in Figure 10a. Interactions between adjacent tapesare assured by cooperativeπ-π stacking involving the phenresidues coordinated to the M centers (Figure 11).

Thermal Analysis. The thermal stability (under a continu-ous air flow) of [M(phen)3][Ge(C2O4)3]‚xH2O [with M2+ )Cu2+ (1a and1b), Fe2+ (2a and2b), Ni2+ (3), and Co2+ (4)]and [MGe(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5)and Cu2+ (6)] was investigated between ambient temperatureand ca. 600°C with the registered thermograms (see FigureS2) clearly evidencing a similar behavior for all compoundsbelonging to a given family.

This study was particularly informative regarding thesubtle composition difference between pseudo-polymorphs[Fe(phen)3][Ge(C2O4)3] (2a) and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b). Indeed, for the latter compound between

(76) Lin, Z. E.; Zhang, J.; Zheng, S. T.; Yang, G. Y.MicroporousMesoporous Mater.2004, 74, 205-211.

Figure 7. Close packing of cationic [Cu(phen)3]2+ fragments in2b along the [100] crystallographic direction, emphasizing the C-H‚‚‚π interactionsbetween neighboring residues. For clarity, only the hydrogen atoms involved in the represented interactions are shown. Geometrical details (approximateC‚‚‚π distances) on structurally relevant C-H‚‚‚π interactions (π represents the centroid of the aromatic ring): C(38)-H(38)‚‚‚π 3.39 Å; C(40)-H(40)‚‚‚π3.66 Å.

Figure 8. Ball-and-stick packing arrangement of2b viewed along thecrystallographic [010] direction. Hydrogen atoms have been omitted forclarity.



ambient temperature and ca. 268°C a small continuousweight loss of about 0.8% confirms the presence of a smallamount of water present in the structure (calculated 0.4 performula unit), which agrees with the structural assumptionsdeduced during the single-crystal X-ray diffraction studies.

Neglecting the initial weight loss of compound2b thethermal decomposition of all compounds can be roughlydivided in two major stages: the first corresponds to releaseof a variable amount of phen ligands, and the second isattributed to decomposition of the [Ge(C2O4)3]2- anions. Itis noteworthy to mention that the first thermal decompositionstarts to settle in for compounds1a and 1b at a lowertemperature (around 205 and 201°C, respectively) than forthe remaining materials (between 268 and 280°C) with thisphenomenon being ascribed to the stronger oxidizing proper-ties of Cu2+ when compared with the remaining transition-metal centers. Nevertheless, in the 200-280°C temperaturerange all materials release some phen ligands, usuallybetween 2 and 3 molecules (1a ca. 2.1;1b ca. 2.5;3 ca. 2.3;4 ca. 2.4). In the case of the Fe2+ compounds all phenmolecules are thermally removed. Upon thermal decomposi-tion of the [Ge(C2O4)3]2- anions, which usually starts to settlein around 300°C, the obtained residues are composed of amixture of metallic oxides which, except for1a (due to thepresence of a small impurity in the as-synthesized material),are in good agreement with the expected stoichiometricquantities: for1b, CuO+ GeO2 (calculated 19.6%, observed20.1%); for 2a and 2b, Fe2O3 + GeO2 (calculated 19.8%and 19.7%, observed 20.0% and 20.6%, respectively); for

3, NiO + GeO2 (calculated 19.2%, observed 19.6%); for4,CoO + GeO2 (calculated 19.2%, observed 20.0%).

The thermal decomposition of compounds5 and6 startswith initial residual weight losses of about 0.6% and 0.5%,respectively, which agrees well with the release of two watermolecules per formula unit (calculated values of ca. 0.5%).This can be attributed to destruction of theµ2 bridges whichinterconnecting the metals within the complex which, asclearly observed in the thermograms, occurs at a significantlyhigher temperature for5 than for6. Interestingly, the sameis observed for the decomposition of the organic componentsof these compounds: while for6, at 600°C, all the materialwas entirely converted into the expected stoichiometric

Figure 9. Schematic representation of the binuclear [CdGe(phen)2(µ2-OH)2(C2O4)2] (5) complex, showing the atom labeling for selected atomsand emphasizing the distorted octahedral coordination environments for theCd2+ and Ge4+ metal centers. Non-hydrogen atoms composing the asym-metric unit are represented with thermal ellipsoids drawn at the 50%probability level. Hydrogen atoms were omitted for clarity. For selectedbond lengths and angles for compounds5 and 6 see Table 9. Symmetrytransformation used to generate equivalent atoms: (i)-x, y, 1.5 - z.

Figure 10. (a) Schematic representation of the parallel packing ofindividual [MGe(phen)2(µ2-OH)2(C2O4)2] complexes mediated byO-H‚‚‚O hydrogen bonds (dashed blue lines) and leading to formation ofa one-dimensional supramolecular tape:∞2[MGe(phen)2(µ2-OH)2(C2O4)2].(b) Magnification of a portion of the supramolecular tape emphasizing theR2

2(12) graph set motif formed between two neighboring complexes andinvolving theµ2-bridging hydroxyl groups and coordinated oxalate anions.Geometrical details on O(5)sH(5A)‚‚‚O(2)i: for 5, d(O‚‚‚O) ) 2.7699-(15) Å with ∠(OHO) ) 170.3(2)°; for 6, d(O‚‚‚O) ) 2.7791(13) Å with∠(OHO)) 168.0(1)°. Symmetry transformation used to generate equivalentatoms: (i)-x, -y, 1 - z. For clarity, only hydrogen atoms involved inhydrogen-bonding interactions are represented.

Figure 11. π-π Interactions (dashed green lines) interconnectingneighboring∞2[MGe(phen)2(µ2-OH)2(C2O4)2] supramolecular tapes. Hydrogen-bonding interactions are represented as dashed blue lines, and hydrogenatoms belonging to the phen residues have been omitted for clarity.

Shi et al.


amount of CuO+ GeO2 (observed residual of 25.5%,calculated of about 26.06%), for5 the decomposition is stilloccurring. The different kinetics associated with the thermaldecomposition of5 and 6 can be ascribed to the distinctphysical-chemical properties of the M metals composing thebimetallic complexes with Cu2+ clearly promoting thedecomposition.

Vibrational Spectroscopy.FT-IR and Raman spectra areparticularly informative regarding the presence of the primarybuilding blocks of the complexes, showing the characteristicbands of phen and oxalate organic ligands, hence fullysupporting the chemical composition and structural detailsdetermined from the single-crystal X-ray diffraction studies.77

Specific band assignments for the most intense and diagnosticbands are collected in the Experimental Section, while theFT-IR spectra are provided as Supporting Information (FigureS3).

A number of bands located between 810 and 900 cm-1

are diagnostic of the presence of coordinated oxalate anionsto Ge4+ and attributed to theν(C-C) and ν(Ge-Ooxalate)stretching vibrational modes. Several intense bands foundin the ca. 1100-1520 cm-1 spectral region are characteristicof a number of vibrational modes of phen. A strong bandcentered at ca. 1735 cm-1, particularly evident in all spectra,strongly supports the existence of uncoordinated (andterminal) CdO groups arising from the coordinated oxalateanions. Moreover, theνasym(-CO2

-) andνsym(-CO2-) stretch-

ing vibrational bands of oxalate groups appear in the 1676-1580 and 1430-1310 cm-1 spectral regions, respectively,which correspond to∆ values between 246 and 270 cm-1,in good agreement with the observedanti,anti-chelatebidentate coordination fashion for these anionic moieties (seecrystallographic description of the structures).78,79

In the case of5 and6, a broad band is markedly visible

above 3300 cm-1 (centered at ca. 3321 cm-1 for 5 and ca.3396 cm-1 for 6) and attributed to the characteristicν(O-H) stretching vibrational band associated with theµ2-bridginghydroxyl groups involved in hydrogen bonds, in accord withthe crystal structure.77

Concluding Remarks

The preparation, via typical hydrothermal approaches, ofthe first bimetallic complexes containing either [Ge(C2O4)3]2-

or [Ge(C2O4)2] with M cationic complexes of 1,10′-phenan-throline (phen) and their full structural description based onsingle-crystal X-ray diffraction investigations has beendescribed. It was shown that the large chemical speciescomposing each complex structure close pack in the solidstate mediated by extensive subnetworks of intermolec-ular interactions which include, among others, strongO-H‚‚‚O and weak C-H‚‚‚O hydrogen-bonding interac-tions, C-H‚‚‚π andπ-π contacts.

Acknowledgment. We are grateful to FEDER, POCI2010, and Fundac¸ ao para a Cieˆncia e Tecnologia (FCT,Portugal) for their generous financial support, funding towardthe purchase of the single-crystal diffractometer, and alsopostdoctoral research grants (no. SFRH/BPD/9309/2002 (toF.-N.S.) and SFRH/BPD/14410/2003 (to L.C.-S.)). We alsothank the EPSRC (U.K.) and the University of Leeds forequipment funding.

Supporting Information Available: Crystallographic informa-tion as CIF files; Le Bail whole-powder-diffraction-pattern profilefitting of [Co(phen)3][Ge(C2O4)3]; thermograms and FT-IR spectrafor all compounds. This material is available free of charge via theInternet at http://pubs.acs.org.

IC700507J

(77) Socrates, G.Infrared Characteristic Group Frequencies-Tables andCharts, 2nd ed.; John Wiley & Sons Ltd.: Baffins Lane, Chichester,1994.

(78) Oldham, C. Carboxylates, Squarates and Related Species. InCom-prehensiVe Coordination Chemistry, 1st ed.; Wilkinson, S. G., Ed.;Pergamon Press: New York, 1987; Vol. 2, pp 435-459.

(79) Deacon, G. B.; Phillips, R. J.Coord. Chem. ReV. 1980, 33, 227-250.



Date post:	03-Jun-2020
Category:	Documents
Upload:	others
View:	29 times
Download:	0 times

Heterodimetallic Germanium(IV) Complex Structures with ... · Heterodimetallic Germanium(IV)...

Documents